The F.B.I. director, James B. Comey, asked the Justice Department this weekend to publicly reject President Trump’s assertion that President Barack Obama ordered the tapping of Mr. Trump’s phones, senior American officials said on Sunday. Mr. Comey has argued that the highly charged claim is false and must be corrected, they said, but the department has not released any such statement.

Mr. Comey made the request on Saturday after Mr. Trump leveled his allegation on Twitter. Mr. Comey has been working to get the Justice Department to knock down Mr. Trump’s claim because there is no evidence to support it and it insinuates that the F.B.I. broke the law, the officials said…

A statement by the Justice Department or Mr. Comey refuting Mr. Trump’s allegations would be a remarkable rebuke of a sitting president, putting the nation’s top law enforcement officials in the position of questioning the truthfulness of the government’s top leader. The situation underscores the high stakes of what the president and his aides have set out by accusing the former president of a conspiracy to undermine Mr. Trump’s young administration…

Along with concerns about the potential attacks on the bureau’s credibility, senior F.B.I. officials are said to be worried that the notion of a court-approved wiretap will raise the public’s expectations that the federal authorities have significant evidence implicating the Trump campaign in colluding with Russia’s efforts to disrupt the presidential election.